Heat exchangers formed from thermoplastic polymers and methods for the manufacture of such heat exchangers are known. For instance, a number of heat exchangers formed from thermoplastic polymers and methods for the manufacture thereof are disclosed in PCT Patent Application WO 91/02209 of A. J. Cesaroni, published Feb. 21, 1991, and in the published patent applications referred to therein. Thermoplastic polymer heat exchangers of a tubular construction are described in U.S. Pat. Nos. 4,923,004, and 5,078,946, issued May 8, 1990 and Jan. 7, 1992, respectively, both of E. L. Fletcher and T. H. Kho, in which tubes are integrally formed with a manifold section in a moulding or similar process. A preferred material of construction for the heat exchangers is polyamide, especially aliphatic polyamide.
While heat exchangers formed from thermoplastic polymers have been fabricated by the techniques described in the above patents and published patent applications, improvement in the construction and methods of fabrication would be beneficial to add further flexibility and economy to the fabrication and use of heat exchangers formed from thermoplastic polymers. In particular, assembly of tubes into headers or manifolds or other structures in the manufacture of tube heat exchangers is usually a tedious and time-consuming process, often involving use of adhesives to bond the tubes into position. The manufacture of heat exchangers from polyamides can pose unique and difficult problems, especially when compared with use of other polymers, but the resultant heat exchangers have many advantages over heat exchanges from other polymers.
A process for connecting bodies having hollow sections e.g. tubes, to moulded bodies made of a thermoplastic polymer is disclosed by H. Gross in U.S. Pat. No. 4, 773,956. A process and apparatus for face welding bundles of thermoplastic polymer mouldings under pressure is disclosed by H. Gross et al in U.S. Pat. No. 4,797,173. The process relates to the face welding of extruded thermoplastic polymer mouldings e.g. tubes, having end faces that lie in a plane. The end faces are pressed against a heatable and coolable plate in which grooves have been formed corresponding to the cross-section of the end face, and the polymer is heated until molten. A hexagonal honeycomb-like structure of tubes is formed. While such a process may be effective in forming honeycomb structures, it is complex and not adapted to inserting tubes into articles.
An efficient and economical method of bonding large numbers of tubes into an article e.g. in the manufacture of a heat exchanger, would be beneficial.